1. Field of the Invention
The present invention relates to a microphone unit which transduces an input voice into an electric signal, and more particularly, to a structure of a microphone unit which is so formed as to allow a sound pressure to act on both surfaces (front and rear surfaces) of a diaphragm and generates an electric signal by using a vibration of the diaphragm based on a sound pressure difference.
2. Description of Related Art
Conventionally, a microphone unit is used in, for example, voice communication devices such as a mobile phone, a transceiver and the like, or in information process systems such as a voice identification system and the like which use a technology for analyzing an input voice, or in a recording device and the like. For over-the-telephone talking, voice recognition and voice recording, it is preferable that only a target voice (user's voice) is collected. For this purpose, a microphone unit which accurately extracts a target voice and removes noise (background noise and the like) other than the target voice is being developed.
As a technology which in a use environment where noise is present, removes noise and collects a target voice only, there is a technology for providing a microphone unit with directivity. As an example of a microphone unit which has directivity, a microphone unit which is so formed as to allow a sound pressure to act on both surfaces of a diaphragm and generates an electric signal by a vibration of the diaphragm based on a sound pressure difference is conventionally known (e.g., see patent documents 1 and 2).
Incidentally, conventionally, a microphone unit is equipped with an electric circuit portion that processes (e.g., amplification process and the like) an electric signal which is generated based on a vibration of a diaphragm. And, conventionally, this electric circuit portion is disposed outside a sound guide space which extends from a sound hole to the diaphragm (e.g., see FIG. 2 of the patent document 2).
[Patent document 1] JP-A-1992-217199
[Patent document 2] JP-A-2005-295278